The invention relates to the manufacture and carding of artificial teeth for dentures. In the manufacture of dentures, it is necessary to select the size and shape of artificial teeth in a compatible manner with the facial characteristics of the patient. In the manufacture of artificial teeth, the artificial teeth are identified by mold shade, and type of material they are made from. Typically the manufactured teeth are placed in a set on a tooth holder commonly called a card and are identified by the mold and shade of the teeth. The tooth card may hold a set of related artificial teeth like a set of anterior or posterior, upper or lower teeth. A dental laboratory orders and receives a set of artificial teeth on the card. The carded teeth may be used to display the teeth to the patient and the dental lab technician works from the carded teeth to fashion and make the dentures in accordance with the prescription.
Various ways of retaining the artificial teeth on the card have been known. It has been quite common, in connection with tooth cards, to provide either a strip or panel of wax, preferably of a somewhat tacky nature, to which the artificial teeth are affixed by various means, including the pins normally projecting from the pin-shelf of anterior porcelain artificial teeth, for example. Such pins are embedded in the wax of the holder and it is convenient to handle artificial teeth of this type in related sets such, for example, as six anterior teeth respectively comprising left and right canine teeth at opposite ends of the set, left and right lateral teeth, inward from the latter, and left and right central teeth in the center of the set of teeth. Usually, a set of such upper anteriors is mounted on one card and a corresponding set of lower anteriors will be mounted on a separate card, in accordance with customary practice.
Posterior artificial teeth, such as the first and second molars, and first and second bicuspids, including both left and right of each, will be mounted on a tooth card in sets of eight, respectively for upper and lower dentures.
When these sets of related teeth are prepared upon such tooth cards by a manufacturer, the assembled teeth in each set usually have either identical or closely related shades, and the proportion, shape and size (mold) are related so that, with the other characteristics, they are rendered as close as possible in appearance to natural teeth which they are to replace.
After the dentist makes an impression of the patient's mouth and the teeth have been selected, the impression and prescription are sent to a dental laboratory. The dental laboratory then makes up a model of the patient's mouth according to the impression and attaches the prescribed teeth to the model by means of a wax base plate. The resulting unit is called a "try in" which unit is sent to the dentist who tries the unit in the patient's mouth. Upon satisfactory approval, the "try in" unit is then sent back to the dental laboratory. At the dental laboratory, a plaster mold is made of the "try in" unit. The artificial teeth stay in the plaster mold and the wax base plate is boiled out. A suitable plastic such as acrylic is then filled in the space that the wax plate previously occupied. Next, the acrylic material is processed by heat, then it is broken out of the plaster, leaving the denture. The same process is followed for both upper and lower dentures.
In affixing the artificial teeth to the acrylic material, it is necessary to provide a means of either mechanically or chemically connecting the two together. Heretofore, in the case of porcelain anteriors, the teeth are provided with pins having pinheads which are embedded in the acrylic material. The porcelain posteriors are typically provided with a diatoric hole. Various plastic materials and compositions have also been utilized in the manufacture of artificial teeth such as acrylic and acrylic compositions. In the case of plastic artificial teeth, the teeth are typically provided only with a mating surface which is adhered to the acrylic material of the denture base by chemical bonding. No mechanical retention is provided.
In securing teeth to a tooth card, porcelain teeth are typically secured on a card with wax material which retains the teeth. In repairing a set of dentures made of porcelain teeth, the replacement teeth have wax material left on the base of the teeth. The wax material creates a problem in adhering to the tools and hands of the technician. The wax material comes in various colors and is difficult to completely remove from the teeth. The colored wax material often shows up on the "try in" model which is not a pleasing appearance to the patient resulting in a not entirely satisfactory display or process. Considerable time and effort is required to completely remove the wax material from the teeth. This may be done by cleaning the material off with a knife or by enflaming and then wiping the teeth clean with a cloth. In either case, due to the time and effort involved, this is typically not carried out resulting in the above mentioned problems. U.S. Pat. No. 3,018,884 shows a conventional method for carding teeth by means of a wax card.
Another problem with the wax card is that the plastic and porcelain teeth are not always retained well by the wax material causing the teeth to fall off of the card presenting a problem of loose teeth and difficult identification. This is particularly true in extreme hot summer and cold winter weather when the wax becomes extremely hot and extremely cold.
Plastic, i.e. acrylic, teeth are also typically carded on wax cards. Due to the absence of any holes or pins on the plastic teeth, the problem of cleaning the wax material from the plastic teeth is not quite as accute. However, because there is no retention by pins or holes the plastic teeth are not as securely retained on the wax cards and are more likely to become loose.
Various carding devices have been proposed for artificial teeth by which teeth may be mechanically retained on the card such as shown on U.S. Pat. Nos. 1,248,030; 675,044; 691,551; 2,111,095; and 1,573,858. The above mentioned carding devices have not been entirely satisfactory, partially for the reason that the corresponding retention part of the tooth has required openings to be formed in the teeth which leave thin, weakened tooth areas susceptible to breakage and are not entirely satisfactory. Further, the retention often requires a tedious manual maneuvering of the artificial teeth on the mechanical retention part in order to take the teeth on and off. The artificial teeth may be easily dislodged from some of the mechanical retention features.
U.S. Pat. No. 2,302,376, and 2,334,214 disclose carding devices for artificial teeth in which anterior teeth are placed by wax retention on a holder to be placed in a patient's mouth for determination of a satisfactory appearance.
In the anchoring of plastic teeth to the denture base, if a good chemical bond is had between the acrylic denture base and the plastic teeth, then problems are normally not encountered. However, due to the lack of any mechanical innerlocking features, plastic teeth may easily dislodge from the denture base if a good chemical bond is not had.
Artificial porcelain teeth have been provided with different openings, holes, and other mechanical features to anchor them to the denture base material. For example, artificial teeth are shown in U.S. Pat. No. 200,284, disclosing very early the formation of openings in artificial teeth, which openings are used to retain the teeth on the denture base material. However, in this early stage of the art, the compatibility of the teeth for purposes of carding the teeth was not a consideration. Teeth of this type may be considerably more difficult to card.
U.S. Pat. No. 2,600,496 discloses anchorage for plastic artificial teeth in which teeth are disclosed with metal embedded in the teeth for purposes of anchoring the teeth. These type teeth are considerably more complicated and expensive to manufacture than the present day porcelain and plastic, and are more difficult to card.
U.S. Pat. No. 411,272 discloses artificial teeth embedded in a denture base by means of spring clips. This very early method of securing teeth was particularly for securing teeth to vulcanite material which is a rubbery base material having particular retention problems.
U.S. Pat. No. 691,550 discloses anchoring teeth in a wax card by using a wire loop which extends into the diatoric hole. This type anchor is very susceptible to becoming loose. U.S. Pat. No. 675,044 proposes mounting of diatoric teeth by wiring them on a rigid strip.
Accordingly, an object of the invention is to provide an improved carding system and method for carding and manufacturing of artificial teeth and dentures in which artificial teeth are retained without wax.
Another object of the invention is to provide a carding system for artificial teeth wherein artificial teeth may be manufactured and carded in a systematic automated way including extrusion, printing, coding, cutting individual card lengths.
Another object of the invention is to provide a card for artificial teeth that can be utilized in an automated manner so that the artificial teeth on a card can be automatically loaded on a card as the artificial teeth are molded.
Another object of the invention is to provide a card for carding artificial teeth that uses less material to manufacture, is reusable, and with a universal product code printed on the base of the card, the card may be used for automated inventory, invoicing, ordering, and reordering by automatic reading of the universal product code.
Another object of the invention is to provide artificial teeth having a design for both porcelain and acrylic materials that is compatible with the carding system of the present invention and also gives equal or superior retention in the denture base material, which is particularly a problem with plastic teeth.
Another object of the invention is to provide a card without wax that will retain present porcelain anterior teeth with pins.
Another object of the invention is to provide a card and carding system for artificial teeth that securely retains the teeth so that only minimal packing material is required for shipping, if at all.
Still another object of the invention is to provide a card and carding system for artificial teeth that will hold the teeth in relative proximity so the card may be manually picked up with the teeth on the card and placed alongside the edentelous area to determine if the teeth are the correct length and size to suit the edentelous area.
Yet another object of the invention is to provide a card and artificial teeth wherein the carded teeth may be individually removed and reattached to the card without disturbing the remaining teeth on the card.